Lighting fixture including two reflectors

ABSTRACT

A luminaire optical system ( 10 ) for an indirect light source including a tubular lamp ( 12 ) having a longitudinal axis ( 22 ), a first reflector assembly ( 14 ) extending parallel to and radially spaced directly above said lamp and a second reflector assembly ( 16 ) parallel to and radially spaced from said lamp directly below the lamp. Each of the assemblies includes symmetrical reflectors ( 22; 24; 30; 32 ) joining in an apex ( 26; 34 ) directly below and above the lamp. The bottom reflector ( 16 ) further may include two segments ( 30   a;    30   b;    32   a;    32   b ) on each reflecting surface, the segments marking a sharp change in reflecting angle. Most such luminaires will typically also include perforations to maintain useful light profiles. The luminaire according to the present configuration increases the lighting efficiency by minimising any reflections passing back into the tube and ensuring an even spread of light throughout an area being illuminated.

The present invention relates to a lighting fixture and in particular toa lighting fixture for a fluorescent lamp which is suspended from ormounted on a ceiling above an area to be illuminated.

BACKGROUND OF THE INVENTION

There are typically two types of light sources, those that emanate froma single point source like incandescent globes, and those that emanatefrom linear sources such as fluorescent tubes.

Linear type light sources generally provide a broader area ofillumination than do point sources of equal intensity and numerousluminaires or fixtures using linear type light sources have come intoexistence, especially those that house fluorescent tubes. Typicallythese are mounted in ceilings although wall mounted luminaires have alsocome into existence. The fixture mounted on the ceiling includes ahousing having two ends, in between which is suspended a fluorescenttube. Since one of the difficulties experienced in such an arrangementis that there is a high glare factor, that is, the light emanatingdirectly from the tube is bright compared to the surroundings, most suchfixtures simply alter the direct light by diffusion through a lens or bydiffuse reflection. Whilst this overcomes the problems of glare, a highpercentage of the total light is lost, with the efficiencies of some ofthe luminaires being below 50%.

Some luminaires propose reflecting the light above the tube towards theceiling. This arrangement does provide indirect ceiling light but isstill relatively inefficient and results in uneven downward lightillumination.

Other luminaires include curved or angled inner surfaces that spread thelight more broadly generally upwardly but the distribution of light isstill limited by the rectangular perimeter of the housing. Yet otherscause the light to be distributed at generally low angles to the ceilingthat also does not provide a even distribution of light.

Accordingly, the applicant is not aware of any luminaire that is highlyefficient, and maintains a broad area of illumination generally belowthe luminaire.

It is an object of the present invention to propose a luminaire thatovercomes at least some of the abovementioned problem or provides auseful alternative to luninaires currently known.

It is a further object of the present invention to propose a luminairethat maximises efficiency and provides good glare control.

SUMMARY OF THE INVENTION

Therefore in one form of the invention there is proposed a luminaireoptical system for an indirect light source including:

-   a tubular lamp having a longitudinal axis;-   a first reflector assembly extending generally parallel to and    spaced above said lamp, said first reflector assembly including a    pair of first reflectors joined to form a first apex;-   a second reflector assembly extending generally parallel to and    spaced below said lamp, said second reflector assembly including a    pair of second reflectors joined to form a second apex, each of said    second reflectors including two arc segments joined at a middle    apex; and-   wherein said first apex, said second apex and lamp longitudinal axis    are axially aligned along a first plane.

In a further form of the invention there is proposed a luminaire opticalsystem for an indirect light source including:

-   a tubular lamp having a longitudinal axis;-   a first reflector assembly extending generally parallel to and    spaced above said lamp, said first reflector assembly including a    pair of first reflectors joined to form a first apex;-   a second reflector assembly extending generally parallel to and    spaced below said lamp, said second reflector assembly including a    pair of second reflectors joined to form a second apex wherein said    first apex, said second apex and lamp longitudinal axis are axially    aligned in a first plane; and-   each of said second reflectors including a second distal edge on    opposed sides of said second apex, each of said second distal edges    and said lamp longitudinal axis defining planes intersecting said    first plane at substantially 90 degrees on either side of said first    plane.

In preference said first plane is substantially vertical.

In preference said first reflectors are symmetrical about said firstapex.

In preference said second reflectors are symmetrical about said secondapex.

Preferably each of said first reflectors includes a first distal edge onopposed sides of said first apex, each of said first distal edges andsaid lamp longitudinal axis defining planes intersecting said firstplane at substantially 70 degrees on either side of said first plane.

Preferably each of said second reflectors includes a second distal edgeon opposed sides of said second apex, each of said second distal edgesand said lamp longitudinal axis defining planes intersecting said firstplane at substantially 90 degrees on either side of said first plane.

In preference each of said second reflectors includes two arc segmentsjoined at a middle apex.

In preference said middle apex and said lamp longitudinal axis of eachof said second reflectors define a plane intersecting said first planeat substantially 45 degrees on either side of said first plane.

Preferably said luminaire optical system includes a housing adapted tohold said lamp, first reflector assembly and second reflector assemblyin fixed relationship thereto.

Preferably said housing is adapted to suspend from a ceiling.

Preferably said second reflectors include translucent areas.

Preferably said second reflectors include perforated areas.

Preferably said tubular lamp is a tube having a diameter of ⅝ inches(equivalent to approximately 1.5875 cm).

Preferably said first reflector assembly first apex is positioned some 1and ¾ inches (equivalent to approximately 4.445 cm) from said tubelongitudinal axis.

Preferably said second reflector assembly second apex is positioned some1 and ⅛ inches (equivalent to approximately 2.8575 cm) from said tubelongitudinal axis.

In preference said first reflector assembly has a footprintsubstantially greater than said second reflector assembly.

In preference the reflection angle of said first reflectors is some 70degrees from vertical at the first apex and some 125 degrees fromvertical at said first distal edge.

In preference the reflection angle of said second reflectors is some117.5 degrees from vertical at the second apex and some 11.25 degrees atsaid second distal edge.

In preference said middle apex is generally in the range of some 3–40degrees.

Although the above description related to a linear light source it is tobe understood that the present invention could equally well be appliedto a point light source. In such an arrangement the bottom and topreflectors would instead of being of a linear configuration be of acircular configuration.

Furthermore it is to be understood that in the case of a linear sourcethat the housing need not have two ends whose purpose is to provide thesupport of the tube, but that the housing simply be able to support thetube above an area to be illuminated. It may therefore be that asuitable design may even include a one-end support.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several implementations of theinvention and, together with the description, serve to explain theadvantages and principles of the invention. In the drawings,

FIG. 1 is a perspective schematic view of a luminaire embodying thepresent invention;

FIG. 2 is an exploded perspective view of the luminaire of FIG. 1;

FIG. 3 is a cross-sectional view of the luminaire of FIG. 1; and

FIG. 4 is a cross-sectional view as in FIG. 3 but illustrating thereflection of individual light rays.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following detailed description of the invention refers to theaccompanying drawings. Although the description includes exemplaryembodiments, other embodiments are possible, and changes may be made tothe embodiments described without departing from the spirit and scope ofthe invention. Wherever possible, the same reference numbers will beused throughout the drawings and the following description to refer tothe same and like parts.

Referring now to the drawings and in particular to FIGS. 1 to 3, thereis shown simplified schematic views of a lighting fixture or luminaire10 including a tube 12 a first reflector assembly 14 and a secondreflector assembly 16. Sides 18 and 20 located on opposite ends of theluminaire are used to keep the structure integral and to, for example,suspend the luminare from the ceiling.

The first reflector assembly 14 is positioned above the tube 12 andincludes two parabolic reflectors 22 and 24 joined at first apex 26, thefirst apex 26 positioned generally directly above the longitudinal axis28 of the tube 12.

The second reflector assembly 16 is positioned directly below the tube12 and includes two reflectors 30 and 32 joined at a second apex 34, thesecond apex 34 positioned generally directly below the longitudinal axis28 of tube 12.

It will now be readily apparent to the reader that the first apex 26,longitudinal axis 28 and second apex 34 all lie on a first plane, theplane being generally vertical when one is considering a luminaire thatis mounted to or hung from a ceiling. Although not shown it is to beunderstood that the luminaire is generally mounted to the ceiling byappropriate fixing means and includes the necessary electricalcomponents including power supply and ballast.

Typically the reflector assemblies are symmetrical. However, when theluminare may be applied to an atypical situation, such as being mountedproximate a wall, where one is desirous of maintaining efficiency in onedirection only and gently illuminating a wall in the other, theassemblies may in fact not be symmetrical but will be modified toaccommodate the particular situation.

The footprint of the first reflector assembly 14 is substantiallygreater than the second reflector assembly 16 so that light that isproduced by the tube 12 is reflected pre-dominantly downwards.

Both the first apex 26 and the second apex 34 ensure that emitted lightfrom the tube 12 is substantially reflected outwardly from the luminaire10 or at least towards one of the reflecting surface assemblies ratherthan being reflected back into the tube 12 where it would be lost thusreducing the total illumination efficiency of the luminaire. Thus, it isthe relative geometry of the luminarie that will achieve this resultwith each configuration having a unique solution, but each configurationhaving at the very least a first refector assembly with a largerfootprint than the second and each assembly having an apex that liesdirectly below or above the tube. One particular configuration will bediscussed shortly.

Those skilled in the art will appreciate that this size differentialresults in a larger percentage of light being reflected generallydownwardly whether reflected straight from the tube 12 or whether it isa primary or secondary reflection after light has first been reflectedfrom reflector assembly 14. The skilled addressed will now alsoappreciate that to minimise total light intensity loss one wants tominimise total reflections that a light ray may undergo prior topropagating generally downwardly out of the luminarie. The use of thefirst and second reflector assemblies means that with the rightgeometrical shape of the reflectors the substantial percentage of lightgoes through not more than two such reflections. Theoretically it mayeven be possible that all of the light goes through no more than tworeflections, much depending on the accuracy of the manufacturingprocess.

This is further aided by each of the reflecting surfaces 30 and 32 ofthe second reflector assembly 16 being composed of two arc segments,surface 30 comprising segments 30 a and 30 b and surface 32 comprisingsegments 32 a and 32 b. The segments 30 a and 30 b join in a middle apex36, segments 32 a and 32 b join in middle apex 38. The middle apexchanges the angle of reflection quite markedly by a figure approachingsome 50 degrees.

The distal edges 40 and 42 of the first reflectors 22 and 24respectively of the first reflector assembly extend substantiallyhorizontally above the tube 12 so that the distal edges and said tubelongitudinal axis define planes intersecting said vertical plane atsubstantially 70 degrees on either side of the vertical plane.

The distal edges 44 and 46 of the second reflectors 30 and 32respectively of the second reflector assembly extend below the tube 12so that the distal edges and said tube longitudinal axis define planesintersecting said vertical plane at substantially 90 degrees on eitherside of the vertical plane. This ensures that there is no directdownwards light from the tube that would result in glare.

The apex is positioned at 45 degrees to the tube, that is, the middleapex and lamp longitudinal axis define a plane intersecting saidvertical plane at substantially 45 degrees on either side of thevertical plane.

When referring to FIG. 4, the reader can now appreciate that theparticular geometric configuration of the reflector assemblies leads tovery little, if any, of the reflected light passing back through thetube thus increasing the efficiency of the luminaire.

In the particular case when one is using a T5 type tube the followingtable provides approximate geometrical estimates of the surface anglesat various angles form the vertical plane. This assumes that the firstreflection assembly is some 1 and ¾ inches above the tube centre whilstthe bottom reflector is some 1 and ⅛ inch below.

Top reflector Reflector surface angle from Angle from lamp vertical  0° 70° 25°  0° 50° 115° 70° 125°

It is to be understood that the curvature in between the angles above isof a smooth transitional type with no sudden angle changes. Accordinglyin most instances the curvature would vary in the range of some 0.5° to1° with every degree change in the angle from the tube.

Bottom reflector Reflector surface angle from Angle from lamp vertical 0° 117.5°  5° 112.5° 20°   105° 25°   100° 30°  97.5° 45° Apex anglearound 30°–35° 50° 51.25° 90° 11.25°

In the case where the tube is of a different diameter, or where onewishes for a different light distribution, the sizes, distances, andcurvature of the reflectors may be changed to accommodate the situation.

In cases where there may be a need for greater direct downwardillumination, one may include apertures or slits in the bottom reflectorwhere some radiated light projected downwardly is not reflected throughany surface. A reflector may include a mixture of circular apertures andlongitudinal slits distributed in a pattern through the reflector.

Those skilled in the art will now appreciate that use of reflectorssymmetrically disposed below and above the tube wherein the topreflector is of a greater cross-sectional size than the bottom one andwhere the curvature of the two reflectors is relatively chosen resultsin a luminaire with a greater light efficiency than hitherto known.

The reflectors are typically coated with a reflecting surface having ahigh efficiency of reflection and that acts as a mirrored surface.However those skilled in the art will appreciate that the surfaces ofthe reflectors may include different coatings and/or filters that maynot only control the reflection percentages but also change itscharacteristic. The reflecting surface may also include individual microspecular reflectors whose orientation may vary slightly to achieve amore homogenous distribution of light.

One can now appreciate that the present invention teaches the use ofupper and lower reflectors with high reflectivity and specularreflective surfaces that are designed to interdependent geometry thatmaximises efficiency by minimising light loss and the number ofreflections required to exit the fixture while providing good glarecontrol by covering the tube form view.

The lower reflector is generally perforated to avoid contrast at thereflector edge and to provide a good light output profile. The conceptis adapted to any diameter tube and to general or specific purposefixture as well as other types of light source.

As discussed above it is to be understood that the present invention canbe applied to a point light source. In such an arrangement, thereflectors assume a circular symmetry instead of the linear symmetry asdiscussed above.

Further advantages and improvements may very well be made to the presentinvention without deviating from its scope. Although the invention hasbeen shown and described in what is conceived to be the most practicaland preferred embodiment, it is recognized that departures may be madetherefrom within the scope and spirit of the invention, which is not tobe limited to the details disclosed herein but embraces all equivalentdevices and apparatus.

1. A luminaire optical systems for an indirect light source including: atabular lamp having a longitudinal axis; a first reflector assemblyextending generally parallel to and spaced above said lamp, said firstreflector assembly including a pair of first reflectors joined to form afirst apex; a second reflector assembly extending generally parallel toand spaced below said lamp, said second reflector assembly including apair of second reflectors joined to form a second apex, each of saidsecond reflectors including two arc segments joined at a middle apex;and wherein said first apex, said second apex and lamp longitudinal axisare axially aligned along a first plane.
 2. A luminaire optical systemfor an indirect light source including: a tubular lamp having alongitudinal axis; a first reflector assembly extending generallyparallel to and spaced above said lamp, said first reflector assemblyincluding a pair of first reflectors joined to form a first apex; asecond reflector assembly extending generally parallel to and spacedbelow said lamp, said second reflector assembly including a pair ofsecond reflectors joined to form a second apex wherein said first apex,said second apex and lamp longitudinal axis are axially aligned in afirst plane; and each of said second reflectors including a seconddistal edge on opposed sides of said second apex, each of said seconddistal edges and said lamp longitudinal axis defining planesintersecting said first plane at substantially 90 degrees on either sideof said first plane.
 3. A luminaire optical system as in any one ofclaims 1 or 2 wherein said first plane is substantially vertical.
 4. Aluminaire optical system as in claim 1 wherein said first reflectors aresymmetrical about said first apex.
 5. A luminaire optical system as inclaim 1 wherein said second reflectors are symmetrical about said secondapex.
 6. A luminaire optical system as in claim 1 wherein each of saidfirst reflectors includes a first distal edge on opposed sides of saidfirst apex, each of said first distal edges and said lamp longitudinalaxis defining planes intersecting said first plane at substantially 70degrees on either side of said first plane.
 7. A luminare optical systemas in claim 1 wherein each of said second reflectors includes a seconddistal edge on opposed sides of said second apex, each of said seconddistal edges and said lamp longitudinal axis defining planesintersecting said first plane at substantially 90 degrees on either sideof said first plane.
 8. A luminaire optical system as in claim 2 whereineach of said second reflectors includes two arc segments joined at amiddle apex.
 9. A luminaire optical system as in claim 1 wherein saidmiddle apex and said lamp longitudinal axis of each of said secondreflectors define a plane intersecting said first plane at substantially45 degrees on either side of said first plane.
 10. A luminaire opticalsystem as in claim 1 including a housing adapted to hold said lamp,first reflector assembly and second reflector assembly in fixedrelationship thereto.
 11. A luminaire optical system as in claim 10wherein said housing is adapted to suspend from a ceiling.
 12. Aluminaire optical system as in claim 1 wherein said second reflectorsinclude translucent areas.
 13. A luminaire optical system as in claim 1wherein said second reflectors include perforated areas.
 14. A luminaireoptical system as in claim 1 wherein said tubular lamp is a tube havinga diameter of ⅝ inches (equivalent to approximately 1.5875 cm).
 15. Aluminaire optical system as claim 5 wherein said first reflectorassembly first apex is positioned some 1 and ¾ inches (equivalent toapproximately 4.445 cm) from said tube longitudinal axis.
 16. Aluminaire optical system as claim 5 wherein preferably said secondreflector assembly second apex is positioned some 1 and ⅛ inches(equivalent to approximately 2.8575 cm) from said tube longitudinalaxis.
 17. A luminaire optical system as in claim 1 wherein said firstreflector assembly has a footprint substantially greater than saidsecond reflector assembly.
 18. A luminaire optical system as in claim 6wherein the reflection angle of said first reflectors is some 70 degreesfrom vertical at the first apex and some 125 degrees from vertical atsaid first distal edge.
 19. A luminaire optical system as in claim 2wherein the reflection angle of said second reflectors is some 117.5degrees from vertical at the second apex and some 11.25 degrees at saidsecond distal edge.
 20. A luminaire optical system as in claim 1 whereinsaid middle apex is generally in the range of some 3–40 degrees.